Trip-free circuit breaker



Nov. 22, 1960 M. B. WOOD TRIP-FREE cmcurr BREAKER Filed Nov. 18, 1958 MMM Lu. z I 0 l1 6 w N 4 2 60 F J2 4 M 4 6 w 6 E M 1 w! Fllh 3 I46 ,2 1a46 I Inventor Morrz's B. Wood .By his Attorney United States Patentcmcrnr BREAKER Morris B. Wood, Newburyport, Mass, assignor to WoodElectric Corporation, a corporation of Massachusetts Filed Nov. 18,1958, Ser. No. 774,774

6 Claims. (Cl. 200-116) The present invention relates to improvements inelectrical circuit breakers, particularly of the trip-free type whichalso are automatically reset, so that the operating position is alwaysindicated by an operating handle or button regardless of whether it istripped by hand or by anoverload in the circuit passing through it. Moreparticularly the invention relates to improvements in a breakerdisclosed in an application for United States patent, Ser. No. 721,134,filed March 13, 1958 in the name of Lawrence W. Brackett.

The circuit. breaker of the application above noted is an improvementover that disclosed in United States Patent No. 2,613,296, granted June24, 1949, upon application of the present inventor. In the patent asingle fixed and a single movable contact are provided for cooperationin opening and closing a circuit and a thermostatic latch is arranged torelease a contact retaining member whenever an excessive current flowsfor a sufficient period of time to heat the latch above a releasingtemperature. The circuit breaker of the application is an improvementover the construction of the prior patent because it provides a doublebreak instead of a single break, as in the patent, thus increasing thedurability of the breaker and the factor of safety under which itoperates without adversely affecting the external dimensions or thereliability of the constructional features.

The purpose of the present invention is to simplify the constructionalfeatures of the breaker disclosed in the application by reducing theexternal dimensions, increasing the ease of assembly and improving theinsulating values while maintaining the double break, trip free andautomatic reset features of the prior application. These features areembodied in the provision of a trip free overload breaker having a splitrectangular frame formed with a pair of opposed hollow insulatingshells, a fixed contact secured in each shell, a releasable leverextendingbetween the shells, an abutment on the releasable lever,

two resilient arms, one end of each arm being secured within one of theshells and the other end of each arm being disposed opposite to andbiased in spaced relation from the fixed contact inthe correspondingshell, a movable contact secured to the spaced end of each resilient armand a manually operable wedging abutment arranged to act between theabutment on the releasable lever and both resilient arms, simultaneouslyto open and to close the contacts, in combination with a U-shapedbimetallic plate, each side of which is secured to each shell and to oneof the resilient arms and the base of which U- plate forms a latch forretaining the releasable lever. By this construction the entireassemblage is contained between the shells of the frame and each shellforms a mounting for each fixed contact to maintain alignment ofthecorresponding movable contact therewith. Such constructionfacilitates assembly and improves reliability in subsequent use.Preferably, the two pairs of contacts are compartmentized by aninsulating sheet extending between the sides of the bimetallic latch.

of Fig. 4, illustrating a circuit breaker embodying the features of thepresent invention with the contacts in circuit closing positions;

Fig. 2 is a similar view of the circuit breaker shown in Fig. l with thecontacts thereof in open circuit positions;

Fig. 3 is a perspective detail view of the breaker with the contacts anda U-shaped bimetallic plate contained in the circuit breaker; and

Fig. 4 is a sectional plan view of the breaker taken along the lineIV-IV of Fig. l.

The trip-free overload circuit breaker illustrated in the drawings ismanually operated to close or open a circuit to be controlled and isactuated automatically to open and to'prevent holding the circuit closedunder conditions of overload until the conditions are corrected. Themechanism for actuating the breaker is the same in many respects as thatof the prior patent and application, in that a locked releasable memberand a contact actuating member are sepaarted from each other to closethe circuit to be controlled by a wedging member connected to a manuallyoperable button, the breaker.

For convenience in manufacture and assembly the breaker has a splitrectangular frame formed with a a pair of opposed hollow insulatingsimilar shells 2 and 4 riveted or bolted at 6 with open sides together.Within each shell 2 there is located a fixed contact 8. To hold the twofixed contacts in place terminal strips 10 and 12 have the contacts 8welded to them. The terminal strip 10 is bent into a C-shape at one endto surround a similar shaped cavity in the wall of the shells 2 and theterminal strip 12 is bent correspondingly to surround a C- shaped cavityin the shell 4. The terminal strip 12 is longer than the strip 10 toenable it to run along the inside base of the shell 4, so that bothstrips may pass through slots in the bases of the shells at positionsarranged in staggered relation to each other, and may proof eachdisposed opposite to and biased in spaced relation from the fixedcontact 8 in the same shell. Secured to the spaced free end of eachresilient strip is a movable contact 16. The movable contacts and theresilient arms are connected together so that when one end of one arm ismade fast to a shell inner wall the corresponding end of the other oneprojects out of the shell in a position where it will line up with thecorresponding wall of the other shell when brought into assembledrelation. Thus, if a resilient arm is made fast to the inner wall of theshell 2 the other resilient arm will line up with the inner wall of theshell 4 when brought into assembled relation therewith.

To actuate the movable contacts the wedging abutment comprises a pair ofinsulating rolls 18 acting between the releasable abutment, in the formof a pair of insulating rolls 20, and the resilient arms 14. The rolls18 are rotatably mounted at the free end of a link 22 pivoted by a pin24 at its other end on a manually operable plunger button 26. Theplunger button 26 has projecting from I I an enlarged head forconvenient manipulation and is slidingly mounted in a threaded sleeveportion of a cover plate 28. The cover plate 28 has four corner flanges,one of which is shown at 30, bent at right angles to its main body intocontact with the outer faces of the shells 2 and 4, the rivets 6entering the flanges of the shells opposite the terminal strips 10 andH2.

The wedging rolls 18 are secured to opposite ends of a pin 32, passingthrough spacers 34 (see Fig. 4) and being made fast along its centralportion to the link 22. The lengths of the spacers 34 are such as tobring the rolls as into line with the resilient arms 14 and the rolls20, which are released through the flow of an .overload or otherexcessive current flow through the contacts.

To mount the abutment rolls 20 releasably they are secured to theopposite ends of a pin 36 having its central portion made fast to onearm of a lever 38 fulcrumed on a pin 40 supported, in turn, at its endsin recesses in opposite shells 2 and 4. Surrounding the pin 40 at bothsides of the lever 38 are the coils of a torsion spring 42 havingterminal arms engaging the inner sides of the shells and a reverselybent central part engaging the lever to swing it against the sides ofthe shell walls,. When the wedging abutment rolls are pressed betweenthe rolls 20 and the arms 14 the lever is swung away from the sides ofthe shells, as shown in Fig. l and the contacts are closed. To hold thereleasable abutment rolls from I movement while the contacts are beingclosed and to release the abutment rolls an upstanding arm of the lever38 is brought into engagement with a ledge on an angle bar 44 secured tothe base of a U-shaped bimetallic plate 46 of which it forms a part. TheU-shaped angle plate also forms a latch for the releasable lever and isarranged to move away from the upper arm of the lever whenever anexcessive or overload current flows through the contacts 8 and 16.

When an overload current flows through the contacts 8 and 16 and thelatch bar 44 releases the lever 38 the resilient forces of the arms 14move the abutment rolls 20 to positions below the level of the wedgingrolls 18. The contacts 8 and 16 are immediately allowed to open and thewedging rolls 18 are forced upwardly to cause the button to be raisedfrom the position of Fig. 1 to that of Fig. 2. As soon as the button israised the pressure on the abutment rolls is released and the spring 42swings thelever in a clockwise direction to bring its upstanding armagainst the right side walls of the shells 2 and 4. In the correspondingposition of the abutment rolls the contacts may be immediately closed bydownward pressure of the button but if the overload conditions stillpersist the circuit may not be held closed even if the button is helddepressed because the U-shaped bimetallic latch plate releases the lever38 and enables the contacts to be opened regardless of the position ofthe button. It is, therefore, necessary to release the button from itsdepressed position before the contacts may again be closed. This is thestructural distinction identifying the breaker as one of the trip-freeautomatically reset type.

To prevent excessive downward movement of the latch bar 44 so that itwill not engage the upper end of the spring 42 to cause the lever to belatched in an improper position, the shellsZ and 4 have inwardlyprojecting lugs 48, one of which is shown in Figs. 1 and 2. These lugsalso prevent the U-shaped bimetallic plate from moving downwardly tosuch an extent as to interfere with the upward movement of the wedgingrolls 18.

t. For convenience in assembly of the breaker parts within the shells 2and 4 the resilient movable contact carrying arms 14 and the arms of theU-shaped plate 46 are joined together at their ends, as has been stated,each with one of the others and are held together by a rivet 50 passingthrough each of two retainers 52, one end of each resilient arm 14 andthe corresponding arm of the U-shaped bimetallic plate 46. The spacingbetween the shells.

arms of the U-shaped plate then holds the three parts, the arms 14, thearms of the plate 46 and the retainers 52 at exactly the correctrelation to become readily aligned with mountings on the shell walls. Inthis way the entire movable contact assembly is unitized beforeintroducing it within the covering shells, so that much of the assemblywork is completed outside of the shells, thus facilitating manufactureby production methods.

In assembling the breaker a cover plate 28 having a button 26 with alink 22 and wedging rolls 18 attached is presented to the opening wit-hthe U of the U-shaped plate 46. The proper orientation is obtained bytwisting the button to bring the rolls 18 and the plate 46 into therelation of Fig. 2. The plate 28 is slid on the button to contact itshead and thetwo shells 2 and 4 having their terminal strips 10 and 12assembled thereon are applied to either side of the parts thus arranged.In order to introduce the abutment lever 38 between the shells with thepin 40 in a position of alignment with the supporting recesses theshells are cut out along their lower edges and along a portion of eitherside of each. Thus, by using a long nosed plier the pin 40 can beinserted into its recesses in the shells as they are brought together.To hold the shells together the plate 28 is slid along the button awayfrom its head until the four flanges 30 which extend at right angles tothe plate overlap in embracing relation the two upper corners of theWhen this has been done it will be found that the riveted ends of thearms 14 and of the U-shaped plates 46 are confined in cavities 60 formedin the shells 2 and 4, as can best be seen in Fig. 4. The walls of thecavities 60 so confine the arms 14 and the plates 46 that two threadedopenings in each arm end come into sufficiently close alignment with apair of holes in the adjacent side walls of the shells that screws 62may be inserted from the outside without difiiculty. When the screws 62are tightened the movable contact unit is secured permanently in place.All that remains to be done to complete the assembly of the switch is toinsert an L- shaped insulating barrier sheet 64 from the left side ofthe breaker, as shown in Fig. 1 and to apply the rivets 6 to theopenings near the corners of the shells. The barrier sheet 64 not onlyfills the edge cut outs but avoids the possibility of arcing betweenpairs of fixed and movable contacts by separating them and preventingionizing of the air within the confines of the shells. When the rivets 6are driven in the lower corners they secure the barrier sheet in place,holes being formed therein to accept the rivets.

The nature and scope of the invention having been indicated and aparticular embodiment having been described, what is claimed is:

1. A double break trip-free overload circuit breaker having a splitrectangular frame formed with a pair of opposed hollow insulatingshells, a fixed contact secured in each shell, a releasable leverbetween the shells, an abutment on the releasable lever, two resilientarms, one end of each being secured within one of the shells and theother end of each being disposed opposite to and biased in spacedrelation from the fixed contact in the corresponding shells, a movablecontact secured to the spaced end of each resilient arm and a manuallyoperable wedging abutment arranged to act between the releasableabutment and the resilient arms to open and close the contacts, incombination with a U-shaped bimetallic plate, each arm of which issecured to each shell and to one of the resilient arms, and the base ofwhich plate forms a latch for the releasable lever.

2. A double break trip-free overload circuit breaker as in claim 1, inwhich an insulating sheet is secured between the shells and between thefixed and movable contact pairs therein.

3. A double break trip-free overload circuit breaker as in claim 1, inwhich terminals connected to the respective fixed contacts in the shellsprotrude, one from each shell in staggered relation to each other alongens face of the frame.

4. A double break trip-free overload circuit breaker as in claim 2, inwhich the edges of the insulating sheet are exposed along at least twoadjacent sides of the frame and a corner of the frame defined by thesides has a fastening rivet passing through both shells.

5. A double break trip-free overload circuit breaker as in claim 4, inwhich terminals having G-shaped ends, each areconnected to therespective fixed contacts in the shells and protrude from each shell andthe shells each have a similarly shaped recess surrounding said comerfastening rivet, the terminals being separated by the insulating sheetat that corner.

6. A'trip-free overload circuit breaker having a split rectangular frameformed with opposed shells, a fixed contact in each shell, a releasablelever between the shells, an abutment on the releasable lever, resilientarms having one end of each secured to and within one of the shells andthe other end disposed opposite to and biased in spaced relation fromthe fixed contact in that shell, a mov able contact secured to thespaced end of each resilient arm and a manually operable wedging memberarranged to act between the abutment on the releasable lever and theresilient arms to open and close the contacts, in combination with aU-shaped bimetallic plate having spaced arms, each secured to one shelland to a corresponding resilient arm, the base of the bimetallic plateforming a latch for the releasable arm and being disposed atsubstantially right angles to the ends thereof which are secured to theshells.

References Cited in the file of this patent UNITED STATES PATENTS2,287,875 Grober June 30, 1942 2,613,296 Wood Oct. 7, 1952 2,813,188Mascioli et al Nov. 12, 1957

